The present invention relates to a hand power tool—preferably a drill hammer or jackhammer—with a pneumatic striking mechanism that has a hammer barrel which has at least one control opening, through which, in an idle position, air can escape from the hammer barrel and which is closed, in a striking position, by a covering preventing the escape of air.
A hand power tool of this kind with a pneumatic striking mechanism is known, for instance from German Patent Disclosure DE 197 24 531 A1. In the drill hammer or jackhammer described in this reference, an axially displaceably supported hammer barrel is disposed in the power tool housing. An axially reciprocating piston is accommodated in the hammer barrel and is coupled with a striker via an air cushion. A restoring spring, with a restoring force, urges the hammer barrel in the direction of an outset position, in which the air cushion space in the hammer barrel is ventilated via a control opening, so that the striking mechanism of the drill hammer or jackhammer switches to idle, and axial impacts are no longer exerted on a tool. If the hammer barrel is pressed out of this position into the interior of the tool by placement of the tool against a machining point counter to the prestressing of the restoring spring, then the control opening is closed, and the striking mechanism moves to its striking position. As is quite usual for drill hammers or jackhammers, a control sleeve of steel, supported in the power tool housing and closely surrounding the hammer barrel, serves as a covering of the control opening in the striking position of the hammer barrel, and in the striking position, the hammer barrel is thrust under this control sleeve, and the control opening in the hammer barrel is thus covered and closed off from the escape of air. With this kind of control sleeve, the control opening can be closed only inadequately, since there is always a certain sealing gap between the steel control sleeve and the hammer barrel. Thus even in the aspiration phase of the piston, only a limited negative pressure can be built up in the hammer barrel. The efficiency of the striking mechanism suffers as a result. The object of the invention now is to disclose a hand power tool with a pneumatic striking mechanism of the type defined at the outset, whose efficiency is as high as possible.